I want to suppress self-shadowing, but allow to receive and cast shadows otherwsie
Another Very Unsophisticated but simple method that worked for me,
after finish your scene:


Duplicate the desired object
go to Object tab > Cycles setting > ray visability, check 'shadow' for one object and uncheck 'camera ray', do the opposite for the other.


3.flat one of the duplications (the 'shadow') to be plane, face the light source.

I did it in order to save render time.